In many integrated circuits, such as memory devices, it is necessary to have an on-chip reference voltage that is stable over process and temperature variations. As semiconductor technology advances, semiconductor geometries are decreasing. In particular, with the scaling of semiconductor technologies and the use of ultra-thin gate oxides, the demand for low power and low voltage reference circuits is increasing.
In prior art integrated circuits, a band gap reference circuit has typically been used as a general-purpose voltage regulator circuit for supplying a stable voltage reference. However, conventional band gap reference circuits typically cannot operate at power supply voltages less than about 1.0 volts. Thus, as semiconductor technologies advance and as operating voltages decrease, traditional band gap reference techniques may not be adequate.
As a result, there is a need for voltage reference circuits for use in low voltage integrated circuit applications.